Learn Finnish: Onko sinulla varaa ostaa tuo kallis merkkivaate? - Can you afford to buy that expensive designer garment?

This sentence uses the "possessive resource" structure. When expressing that someone has an abstract, uncountable resource (like money or time) to do something, Finnish uses the possessive construction (adessive sinulla + on) and puts the resource noun in the partitive. Here, varaa represents the financial means to do something.

Why is the object tuo kallis merkkivaate in the basic nominative form, rather than the genitive (tuon kalliin merkkivaatteen)?

Because the main clause (onko sinulla varaa) is a possessive sentence, which means it lacks a grammatical subject in the nominative case. When an infinitive (ostaa) is the main action in a subjectless clause like this (or in a necessity sentence like minun täytyy), its total object takes the basic nominative form instead of the genitive.

What is the literal breakdown of the compound word merkkivaate?

It is made up of merkki (mark, sign, or brand) and vaate (garment or piece of clothing). In everyday Finnish, a merkkivaate specifically refers to brand-name or designer clothing.

If I wanted to leave out the verb ostaa and just ask "Can you afford that expensive designer garment?", how would the grammar change?